I upvoted immediately after your first two sentences, and wished I could do it again at the end of your post. Well done.

I've been trying to think of a proper analogy to changing your user agent. Wearing a fake mustache and requesting information from someone publicly giving information to only mustachioed persons?

    You: Can I borrow the book identified by ISBN 1234?
    Librarian: We restrict access to that book to only people who will read it with our page turning machine.
    You: Can I borrow the book identified by ISBN 1234? I am using your page turning machine now.
    Librarian: Sure, here you go.